Three-dimensional printing, also known as additive manufacturing, is a process of making a three-dimensional solid object from a digital model of virtually any shape. Many three-dimensional printing technologies use an additive process in which an additive manufacturing device forms successive layers of the part on top of previously deposited layers. Some of these technologies use inkjet printing, where one or more printheads eject successive layers of material. Three-dimensional printing is distinguishable from traditional object-forming techniques, which mostly rely on the removal of material from a work piece by a subtractive process, such as cutting or drilling.
Many existing three-dimensional printers form the printed objects using one or more build materials with little or no regard to the appearance of the surface of the object. However, some three-dimensional object printers also form two-dimensional printed images on a surface of the three-dimensional printed objects. The printer forms two-dimensional images on the object to improve the aesthetics of the three-dimensional printed object and to convey information such as printed instructions, part labels, barcodes, and the like. Many three-dimensional object printers apply a layer of a primer material to the outer surface of the three-dimensional printed object and form the two-dimensional printed image on the primer layer.
The build material that forms many three-dimensional printed objects can have an adverse impact on the quality of printed images. For example, a hue shift occurs when light passes through a portion of the printed image and scatters through a translucent build material in the object. FIG. 4 depicts an outer layer of build material 448, a primer material layer 450, and a layer of ink in a printed image 454 on the surface of the primer material layer 450. An incident light ray 404 strikes the ink layer 454. Some of the light penetrates through the ink layer 454 and reflects from the primer layer 450 as depicted by the ray 408. However, in the prior art printed object 454, a portion of the light ray 404 penetrates deeper in to the primer layer 450 and build material layer 448. The light ray scatters laterally as depicted by the ray 412. Some of the scattered light, such as the light ray 416, emerges from the surface of the primer layer 450 at a location outside of the printed ink layer 454. In the example of FIG. 4, the ink layer 454 is formed from a magenta ink. The scattered light 416 that emerges from the primer layer 450 also assumes a magenta hue that produces a “hue shift” in the apparent appearance of a region that is outside of the printed magenta ink layer 454.
FIG. 4 depicts the light scattering phenomenon, which is known to the art as the Yule-Nielsen effect. The Yule-Nielsen effect produces the hue shift in the color of the surface of the three-dimensional object. The hue shift changes the apparent color of regions of the three-dimensional printed object that are outside of the printed areas for different ink colors, and may change the appearance of the object in an undesirable manner. Consequently, improved systems and methods that form printed images on the surfaces of three-dimensional printed objects with reduced hue shift would be beneficial.